https://github.com/kurrent-io/KurrentDB/blob/6571669d12b497fe4db6faeb21e2f40f2d1ac5b2/src/KurrentDB.Api.V2/Modules/Streams/Validators/SchemaNameValidator.cs#L18C2-L19C70
This effectively does not allow to use non English based schema name .
what about èéç used in French, äöüß used in German , or just non Latin based character set ?
It should allow the majority of UTF-8 characters ( and why not emojis , just for fun ?)